Advances in plasma processing have provided for growth in the semiconductor industry. In today's competitive market, the ability to minimize waste and produce high quality semiconductor devices gives the device manufacturer a competitive edge. Accordingly, tight control of the processing environment is generally needed to achieve satisfactory results during substrate processing.
Those skilled in the art are aware that the condition of a processing chamber may affect the quality of the semiconductor devices being produced. Accordingly, the ability to accurately qualify a processing chamber may reduce the cost of ownership of the processing tool and reduce waste. In an example, by accurately qualifying a processing chamber, a recipe may be adjusted to account for the chamber condition. In another example, by accurately qualifying a processing chamber, the processing chamber may be maintained in good working condition, thereby extending the life of the chamber and reducing the potential for waste. As discussed herein, the term “qualify a processing chamber” refers to the process of identifying the condition of a processing chamber and on the steps required to bring the chamber into compliance.
A metrology method may be employed to qualify a processing chamber. With a metrology method, an actual metrology tool may be employed to take measurements such as film thicknesses or critical dimensions (CDs) of a substrate. An example of a commercially available instrument that can make such measurements is an ASET-F5x thin film metrology system from KLA-Tencor Corporation. The measurements may be performed before and after the substrate is processed. After the measurement data have been collected, the etch rates and/or CD bias values for a substrate may be determined. From the spatial map of measured etch rates and/or CD bias values, uniformity may be calculated. As discussed herein, uniformity may be calculated by taking the standard deviation of the etch rates and/or CD bias values.
Although the metrology method may provide an accurate method for qualifying a processing chamber, the metrology method can be an expensive and time-consuming procedure. In an example, the task of measuring the CD bias of just a single substrate may take up to one hour. As a result, most measurements may be taken after a substrate lot has been processed instead of between substrates. For this reason, an entire substrate lot may be damaged before a problem may be identified.